1,4-Dihydropyridine compounds of the type represented by the formula: ##STR1## are known in the art. Many of the compounds are reported to have hypotensive and vasodilating properties, e.g. B. Loev, et al, J. Med. Chem., 17, 956-65 (1974). Also taught in the patent literature are compounds in which the nitrogen may be substituted with an alkyl or substituted alkyl group. These compounds are also taught to have activity useful in cardiovascular applications. However, the procedures reported for the preparation of such compounds have been limited in utility as a synthetic method, i.e., a method in which substantial quantities of the desired compound can reliably be prepared. The literature procedures for the preparation of N-alkyl-dihydropyridine compounds are generally of three types: (1) alkylation of dihydropyridine anions, e.g. J. Palecek and J. Kuthan, Z. Chem., 14, 308-9 (1974) and M. Iwanami, et al, Chem. Pharm. Bull., 27, 1426-40 (1979), (2) Hantzsch condensation with alkylamines, e.g. Bossert et al, U.S. Pat. No. 3,647,807, and (3) reduction of alkyl-pyridinium salts, e.g. U. Eisner and J. Kuthan, Chem. Rev., 72, 1-53 (1972). Each method has been found to have limitations as a synthetic procedure. The alkylation reaction is unsuitable, except for the simplest alkyl groups, giving low yields and product mixtures which are difficult to separate. The Hantzsch condensation procedure appears to work only with selected aniline compounds, e.g. A. Sausins, et al, Khim. Geterotsikl Soedin., 493-501 (1980). Thus, this method is not suitable for the preparation of N-alkyl or N-substituted alkyl-1,4-dihydropyridine compounds. Although a patent appears in the literature, U.S. Pat. No. 3,647,807, which purports to teach the preparation of N-alkyl compounds, the principal products have been found by modern spectrometric methods to be actually amino substituted cyclohexene or cyclohexadiene derivatives. The third method, the reduction of alkylpyridinium salts is a multi-step procedure, generally resulting in very poor yields. Thus, an efficient method is desired for the preparation of known cardiovascular agents. In addition, an efficient method for the preparation of N-substituted alkyl-1,4-dihydropyridine compounds was desired in connection with studies for the intramolecular additions to the dihydropyridine ring system.